A vacuum apparatus for performing an etching process, a film forming process or the like in manufacturing various semiconductor devices includes a gas exhaust unit having a valve and a gas exhaust pump. Further, in the vacuum apparatus, a pressure inside a vacuum chamber can be depressurized to a desired vacuum state.
To be specific, a conductance variable adaptive pressure control (APC) valve, a gate valve, a turbo-molecular pump (TMP) as a main gas exhaust pump, a valve and a dry pump as an auxiliary gas exhaust pump are connected to each other in that order from the side of the vacuum chamber, so that the vacuum chamber can be maintained in a high airtight state and a vacuum state. Moreover, there may also be used an APC value having a gate valve mechanism in which the APC valve and the gate valve are integrally formed.
In such vacuum apparatus, airtightness needs to be checked by regularly measuring a leak rate of the vacuum chamber. The leak rate is measured by using a buildup method for measuring a pressure inside the vacuum chamber and monitoring its variation, the chamber being vacuum-exhausted and sealed by exhausting gas therefrom (see, e.g., Japanese Patent Laid-open Application NO. 2003-77898 (e.g., FIG. 4)). In order to measure the leak rate by using the buildup method, the vacuum chamber needs to be sealed. Accordingly, the gate valve (or the APC valve having the gate valve mechanism) is provided at an upstream side of the turbo-molecular pump in a gas flowing direction.
The gate valve and the APC valve having the gate valve mechanism use an O-ring as a seal member for securing an airtight state. However, in the vacuum apparatus for performing processes using a plasma, the O-ring is easily degraded by radicals generated during a dry cleaning process or the like and thus needs to be replaced frequently. A maintenance work of the O-ring requires a long time due to a recent trend towards a large diameter of a gas exhaust line, which leads to an increased downtime of the apparatus.
A main purpose of disposing the gate valve near the APC valve (or the gate valve integrated with the APC valve) at the gas exhaust unit of the vacuum apparatus is to seal the inner space of the vacuum chamber when measuring a leak rate by using the buildup method. However, if the leak rate is measured by another method wherein the gate valve is not required, the number of maintenance works required for replacing the O-ring can be greatly reduced.